Detroit - These were the two investments the Green Bay Packers could not afford to lose. On crutches, Desmond Bishop hobbled through players, equipment and a surge of media. In his shadow was A.J. Hawk - the other mainstay - dumbfounded.

Both inside linebackers suffered calf injuries and did not finish Green Bay's 27-15 win over the Detroit Lions on Thursday.

"I just took off to run," Hawk said, "and it kind of popped on me."

A lot was pinned on Bishop and Hawk this season, nearly $54 million in combined contracts. Green Bay cut loose two reliable veterans at their position. And midway through the Thanksgiving bar fight at Detroit, Bishop and Hawk were gone. The extent of both injuries is unknown.

At Ford Field, it could have been a worst-case, code-red, brace-yourself scenario. Instead, at least for one day, rookie D.J. Smith and Robert Francois assimilated almost flawlessly.

Smith was active in the run game with four solo tackles, Francois grabbed a momentum-changing interception and the Packers' chokehold on the Lions never loosened.

Two backups rendered to the inactive list and/or special teams all season delivered on a national stage.

"In my mind, you never know," Smith said. "It's next man up. You have to keep that going - 'you never know, you never know.' So with the defense, I try to take every rep like it's my last."

Smith replaced Bishop at the end of the first quarter. Francois replaced Hawk midway through the third. Side by side, they manned the cockpit of a game very much in doubt. The Packers held a 14-0 lead but the Lions were in Green Bay territory.

Francois isn't naive. At that precise moment, he knew what Lions quarterback Matthew Stafford was thinking. The ball continued to sail his direction.

Maurice Morris out of the backfield for 8 yards. Brandon Pettigrew over the middle for 7.

"You could see that they were probably trying to tag me, just being the new guy in there," Francois said. "Any team would do that."

After those back-to-back completions, Francois had enough. Stafford tried lofting a pass over Francois' head to Pettigrew down the middle and the quarterback either underestimated the linebacker's vertical leap or flat-out didn't see him.

Francois trampolined into the air to snare the interception. One play later, Aaron Rodgers hit James Jones for a 65-yard Packers touchdown. Happy Thanksgiving.

"For me, it's expected," said Francois, who was inactive the previous five games. "I go out there to make plays. I don't just go out there to be a nobody. It's just a great feeling to make a play like that."

On Smith's first drive, he stuffed Lions running back Kevin Smith for no gain. Bishop's 97 tackles rank second in the NFL, but there wasn't much drop-off in Green Bay's run defense with the rookie. The Lions' trio of backs mustered only 94 yards.

The challenge could've been communication. With Hawk out - taking his headset with him - the Packers were forced to rely on hand signals. This is probably Hawk's No. 1 value to the defense. He gets players in the right position. The foreman of Green Bay's defense was out and the execution didn't seem to suffer.

"From the instant they came in, they were making plays," defensive tackle B.J. Raji said. "Those guys are very smart. They've been preparing like that every week. With limited reps, they needed to be ready if their number was called."

The double duty could be taxing. Both players have served on the scout team while also memorizing game plans.

Smith credited extra film study with position coach Winston Moss. Ultra-productive in college at Appalachian State - he finished as the Division I FCS active leader in tackles (525) - Smith fell to the sixth round in the April draft. In part due to his size - he's listed at a generous 5 feet 11 inches. But also in part due to competition - the NFL is a cut above the Southern Conference.

Francois? The reserve linebacker with a massive tattoo of the Lombardi Trophy on his right forearm has been waiting two seasons. The last time most fans may remember him is Week 6 of last year. That's when he committed a costly (and highly controversial) special-teams penalty in a loss to the Miami Dolphins.

"I don't think people think about that play too much anymore," Francois said, chuckling.

So here they were at Ford Field, keeping the Packers undefeated. Two players that played a combined of three defensive snaps all season. There is no long-term diagnosis on either Bishop or Hawk yet, but Raji is confident in both backups.

"Oh yeah, definitely," Raji said. "We feed off each other so we're ready for anything."